NAVIGATION SYSTEM

To navigate the Stingray to each of the
objectives, the planner node calculates the necessary bearing and depth
that the vehicle needs to maintain in order to get to the target. These
target values are passed to the navigation node where the controls
software performs the command based on sensor data from the IMU and
depth sensor.

Compass

An Ocean server OS-50003-axissolid state
compass is used to determine the attitude of the vehicle. The compass
uses a combination of magnetometers and accelerometers to determine the
angles of pitch, roll, and yaw where the latter is used as a compass
heading. These values are output from the compass as an ASCII stream via
USB.

Depth Sensor

A SSI Technologies P51-15-S-B-I36-4.5V-R
pressure sensor is used to measure the depth of the vehicle relative to
the surface of the water. The 0.5 - 4.5V DC output voltage range
supplied by the depth sensor is measured by using the Labjack data
acquisition card. The depth sensor output voltage corresponds to a
pressure in the range 14.7 - 29.5 psi. Given the finite resolution of
the Labjack voltage measurement, the final resolution of the depth
measurements is within 2.44mm.

Controls Software

In order to maintain target values for pitch,
roll, yaw and depth, the Stingray implements a number of
proportional-integral-derivative (PID) loops. These loops use sensor
data from the IMU, depth sensor, vision, and sonar for feedback to
control each of the propulsion actuators.